Evaluate combination treatment regimens consisting of d4T/NVP/RTV, d4T/3TC/NFV, d4T/NFV/NVP and d4T/3TC/NVP/NFV with respect to their ability to either maintain or reduce a plasma HIV-1 RNA copy number to an undetectable level and to reduce the plasma HIV-1 copy number by > 2 logs at 12 weeks of therapy.